Production of color film having a silver sound track



March 9, 1943. EG E A; 2,313,632

PRODUCTION OF COLOR FILM HAVING A SILVER SOUND TRACK Original Filed Nov. 26, 1937 dahn E gent Hams Fm'e n'c/z Nzssen INVENTORS THEIR ATTORNEYS Patented Mar. 9,1943

monnc'mon or coma mm HAVING A smart sonar 'rnacx John Eggert, Leipzig, and Hans Friedrich Nissen, Dessau, Germany, assignors, by mesne assignments, to General Aniline 8: Film Corporation, New York, N. Y., a corporation of Delaware Original application November 26, 1931, Serial No. 176,668. Divided and this application ctoben 1s, 1940,8erial No. 361,864 g Our present invention relates to the production of color film having a silver sound track. This application is adivisional application of our copending U. S. patent application Ser. No. 176,668, filed Nov. 26, 1937, now Patent No. 2,232,056 of February 18, 1941.

One of its objects is to provide an improved process of producing a color sound film the color 3 Claims. (Cl. 95 2) silver bromide can be converted into silver iodide before the silver is transformed. The developed silver or the sparingly soluble silver iodide-then forms the sound track. When the color pictures are produced by the reversal process the sound track can, f example, be masked during the second expos e of the picture area, the silver removed and the residual sound track consisting .of silver bromide exposed and developed. Or the silver produced in the development of the color picture can be converted into silver chloride, the

paratus constructed in accordance with and embodying a preferred form of our invention.

Figures 2 and 3 are detailed longitudinal sectional views of the apparatus shown in 1. In making picture and sound films in w I h a color photographic proces is used for produc- 1 ing the pictures, the difficulty arisesthat unless special precautions are taken the sound track is also produced in color in the finished film. Since the photoelectric cells of the sound reproducing apparatus do not respond to colored light in the same manner as it does to the contrasts of a black-and-white sound track various diificulties arise in the reproduction of the sound. In particular it is desirable to produce the sound track in silver, since the photoelectric cell is considerveloped by color forming development by subjecting to a fresh exposure, before the removal of the residual silver bromide imag' resulting from the color-forming development, either the By another feature of the invention the sound strip of the film subjected to a calculated exposure, the silver bromide developed to silver and the silver chloride removed by fixing. Another procedure applicable in cases in which the color picture is produced by the reversal process is as follows:

After the second exposure of the picture rec-- 0rd, the film is developed, the residual silver bromide in the sound track is converted into silver iodide, the developed silver is converted into silver chloride or silver bromide and removed by fixing and the silver iodide sound track is blackened by any known process.

steps in these processes are conducted in an after-exposure apparatus in which the film passes around a hollow drum within which is arranged a source of light. The apparatus is preferably specially adapted for the process of the invention by the provision of a drum consisting of interchangeable caydindrical rings hich are respectively transp rent and opaque. The drum is arranged inside a container for liquid preferably constructed of a matt black material.

According to one procedure for producing color pictures on a film having ,a number of superimposed layers adapted for color forming development, there is first produced on said multi-layer film a negative in which-the color are complementary to those of the original; this negative strip of film carrying the sound track or that carrying the picture image, whilst that part of the film which is not to be exposedis masked. For

' example, the silver produced in the color formis then copied on a three-layer positive film and developed in color, the silver precipitate ..is bleached and the filmrfixed. Ii' now the sound track is copied as usual onto the same film and treated in the same manner. as the picture, a color track on a transparent background is ob"- tained. An effective sound track can be obtained in accordance with the invention in the follow- 1 ing manner:

The picture and ound records arepr'inted in the usual manner, the print is developed in color, the silver bleached without removal of the remaining silver bromide, the sound track is exposed a second time, if necessary to a calculated developer and fixed. There are thus obtained a silver sound track and a complementary color sound track. The sound track is preferably printed with light of such color that the color image of the sound track obtained transmits light to which the photo-electric cell is sensitive. In this case the second exposure must be effected so that the silver sound track is produced in the same layer as that in which the color sound track was first produced. In this case therefore the sound track is subjected to a reversal development.

I If the finished color sound film is to be produced by a reversal process and not by printing from a negative, the following method may be used:

The second exposure in the reversal process may be so conducted that the picture image of the film is exposed whilst the sound track is masked by a diaphragm. No silver is then formed in the sound track in the second development. The silver is then dissolved as in the normal reversal process, the sound track consisting of a residual silver bromide image. After dissolution of the silver, the silver bromide in the sound track is exposed and blackened by a further development. The process is completed by fixing the remaining silver bromide and the like in the usual manner,

This process can thus always be used if, in the production of color sound films a second exposure is used and the developed silver is dissolved. In contradistinction to processes in which a coating of a lacquer or the like is used this method of producing the sound track has the advantage that it includes no stage which can lead to contamination of the film or the baths.

In some processes, the silver developed in the picture layer is re-converted into a silver halide, for example, silver chloride. If now the layer were fixed the silver bromide would also be removed and the sound track thus destroyed. Before fixing, therefore, the sound track consisting partly of silver bromide and partly of silver chloride is exposed. The quantity of light is so adjusted that only the silver bromide is rendered capable of development. By development, the sound track is then obtained, whereupon the undeveloped silver chloride can e removed simply by fixing. It is advantageo s to insert in the path of light during the exposure a filter which is opaque to ultra-violet light, which alone renders silver chloride capable of development. In order to avoid fogging the picture it is advantageous to mask the light for producing the final blacken-.

ing so that it fallsonly on the sound track.

A corresponding process for producing a silver sound track is also possible: in the negativepositive process. forming development and the chlorination of the silver the remaining silver bromide can be made capable of development by a renewed exposure without aifecting the chloride. One half of the sound track then consists of 'a; color image, and the other adjacent half of a silver image. Only a negligible quantity of light is absorbed by the dyestuif so that its presence does not interfere with the sound reproduction. If the dyestuff were strongly absorbent a silver sound track For example, after thecolor extent, and the 'print is developed in a usual developer even when unexposed so that the process described is subject to a certain limitation.

In order to carry out the process in spite of this, the following method may be used: Pg

After the color forming development the still undeveloped silver bromide in the sound track is exposed. The silver is thenconverted into silver bromide and subjected to another development. Only the silver bromide which was exposed before the bromination can be blackened by this development. After fixing, a silver sound track is obtained.

Another method is as follows:

If the second development has been conducted without causing development of the silver bromide of the sound track it is possible to convert this bromide into silver iodide. For this purpose use may be made of the known Renwick solution which-contains potassium iodide, sodium sulflte and thiosulfate. It is known that silver iodide is considerably more diflicult to fix than silver chloride or bromide. If the silver still present is then converted into silver chloride or bromide, this can be fixed with the aid of a usual fixing bath. The sound track is then obtained in the form of silver iodide and can be used as such for sound reproduction. It is, however, better to develop this silver iodide or to blacken it, for

example, by sulfiding, so that a silver sulfide.

sound track is obtained. Since only silver iodide is to be blackened, a developer can be used which is relatively powerful, this being necessary because silver iodide is more difficult to develop than silver chloride. i

In order to be able to conduct efficiently the various exposures, namely, the exposure of the sound track without the picture and the exposure of the picture without the sound track, there may be used the exposure apparatus illustrated in the accompanying drawing.

The film I to be illuminated is guided as shown in Figure 1 by guide rollers 2 and 3 around a drum 4, preferably hollow, which has, as it is to be seen in Figure 2, a transparent cylindrical ring 5 and an opaque portion 6. The transparent portion and the opaque portion are interchangeably connected in such a manner that the transparent portion 5 can be exchanged for an opaque portion 6' and the opaque portion 6 for a transparent portion 5 (Fig. 3). These portions may be joined, for example, by a screw thread, bayonet joint or the like. The transparent portion ext ends as far as it is desired that the film should be exposed. The exposure is 'ifected by a lamp 1 in the interior of the drum 4, 5, 6. At the points .at which the film comes into contact with, and

the container .9 in which the whole apparatus is enclosed under water and in which the exposure occurs. Or a strip of black material may be passed through the apparatus in contact with the would be unnecessary, so that in that case the a special treatment of the silver'bromide would be unnecessary. Silver ,chloride is, however, generally already'capable-of being. blackened by a under water in order to obtain good optical contact. In this case the lamp must be protected from the water, for example by means of a glass container. This glass container can be designed to screen ofi false illumination, for example by a metallic reflecting coating. By this means the best possible use is made of the light. If desired, for particular purposes the container may be made of colored glass or provided with a filter layer. 7

What we claim is:

1. In a' process 'ofproducing a silver sound track in color sound film comprising silver halide in which the color images are produced by color development, wherein color formers are reacted with an aromatic color developer, the improvement which comprises exposing said film to produce latent picture and sound images, developing said images and at least said latent picture images by color development, removing the silver formed during development without fixation of silver halide, re-exposing residual silver halide of the sound area only, developing the latent sound images so produced in a black and white out fixation of silver halide, re-exposing only the ver halide by fixation.

3. In a process of producing a silver sound track in color sound film comprising silver halide in which the color images are produced by color development, wherein color formers are reacted with an aromatic color developer, the improvement which'comprises exposing said film to producelatent picture and sound images, color de- 'veloping both said images, removing silver withresidual silver halide of the sound area developing the image so produced in a black and white developer and fixing to remove silver halide.

JOI-IN EGGERT. HANS FRIEDRICH NISSEN. 

